Please provide some exceptions that you mention where the dev does allow anonymous downloads which you're claiming can be downloaded without game ownership.
Nevermind, found it myself
You must be registered to see the links
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Tested it on a game which I don't own and I am still able to download the workshop items so you are correct.
The difference here is now pirates/users who don't have the game on Steam can't download mods that are exclusively on the Steam Workshop unless if the dev allows anonymous downloading.